1. Field of the Invention
The present invention relates to a program down-loading mode for downloading a new program into an information processor having a CPU operable under control of a computer program from an external device.
2. Description of the Related Art
There is a case where an information processor implementing a CPU operable under control of a computer program stored in a memory needs a newer version of its program or updating of the same for executing another processing. Storage of a new program into a memory is implemented by downloading the new program held in an external device via a communication line etc. and writing the program in a memory such as an EEPROM (Electrical Erasable Programmable Read Only Memory).
In downloading a new program into such a device as described above, an abnormal termination of the transfer of the program from the external device or an abnormality occurring in the device itself in the course of the transfer results in an incomplete program stored in the EEPROM or, in some instances the program being destroyed.
One of techniques for preventing such problems caused by an abnormality occurring during the down-loading of a program as mentioned above is recited in, for example, Japanese Laying-Open Patent Application No. 62-60001. Disclosed in the application is the program down-loading implemented, with an operating program stored in an EEPROM, by temporarily storing a program, which is downloaded from an external device, in a RAM (Random Access Memory) as a working area, and then rewriting the current program stored in the EEPROM into the downloaded new program under control of a program for program rewriting stored in a ROM (Read Only Memory), a memory different from the EEPROM. According to this program down-loading mode, since the EEPROM is neither erased nor programmed directly at the time of downloading a new program, it is possible to prevent the program stored in the EEPROM from being incomplete or being destroyed even if the transfer of the program from the external device abnormally terminates or abnormality occurs in the device itself in the course of the transfer.
In the above down-loading, however, because processing is executed under direct control of the program stored in the EEPROM, there is a possibility of malfunction occurring when the contents of the object memory are updated by down-loading during the operation under control of the current program. In downloading a new program in a conventional manner, therefore, it is necessary to stop ordinary processing under control of a current program.